Update friendly_id to latest release
Set the slug value of the html version to previous version

So that a title change does not change the slug
Set slug value of the new_supporting_page to the old one

The slug will be set on create, but set it back to the old slug
Test slug does not change when the html title changes
make the spec title more meaningful
Merge pull request #389 from alphagov/fix-slug-generation-on-new-editions

Set slugs on new editions for supporting pages and html versions

https://www.pivotaltracker.com/story/show/46557791